An oxygen mask apparatus is disclosed in Japanese Patent Laid-Open No. 2005-253925 (to be referred to as “the above-mentioned prior patent literature” hereinafter). In this oxygen mask apparatus disclosed in the above-mentioned prior patent literature, a plurality of rubber string attaching round holes are formed in the left and right end portions of the outer peripheral portion of the mask main body. Therefore, the mask wearer can attach the two end portions of a rubber string to the rubber string attaching round hole in the left end portion and the rubber string attaching round hole in the right end portion of the outer peripheral portion of the mask main body. Accordingly, the mask wearer can wear the oxygen mask apparatus by extending the rubber string over his or her head.
Unfortunately, when using the oxygen mask apparatus disclosed in the above-mentioned prior patent literature, if the mask wearer has no rubber string at hand, he or she must acquire a rubber string by some method. If it takes much labor or a long time to acquire a rubber string, the mask wearer requires an extra labor or extra time before he or she can begin using the oxygen mask apparatus.